Date: Tue, 16 May 2000 06:15:07 -0400 From: Tom Embt <tom@embt.com> To: Greg Lehey <grog@lemis.com>, Ian Cartwright <ICartwright@IT.RJF.com> Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: SCSI Speeds? Message-ID: <3.0.3.32.20000516061507.00de28b0@mail.gfit.com> In-Reply-To: <20000516112057.A10269@freebie.lemis.com> References: <6D5097D4B56AD31190D50008C7B1579B91204C@EXLAN5> <6D5097D4B56AD31190D50008C7B1579B91204C@EXLAN5>
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At 11:20 5/16/2000 +0930, Greg Lehey wrote: >On Monday, 15 May 2000 at 10:23:14 -0400, Ian Cartwright wrote: >> Hello, all. >> >> I have a question regarding the relative speeds of devices on a SCSI bus. I >> have two machines currently running FreeBSD. One is a P-200 with IDE and one >> is a PII-360 with both IDE and SCSI drives. I boot off the the SCSI bus on >> this machine. The IDE drives on both machines are UDMA-33. My SCSI drives >> are as follows (reported by FreeBSD on boot up): ID0: Fast SCSI2 HDD 10.00 >> MB Xfer (Synchronous), ID1: Ultra SCSI2 HDD 40.00 MB Xfer (Synchronous), >> ID2: SCSI2 CD-ROM 10.00 MB Xfer (Async), ID4: SCSI CD-Writer 3.300 MB Xfer >> (Async), ID5: SCSI2 Tape (Xfer not reported, Asynch). >> >> My question is this: why does it seem that the slower machine does disk >> access much faster? When I was installing these machines newfs wrote >> superblocks to the IDE drives much faster than to the SCSI drives, even >> though the Ultra SCSI drive (my FreeBSD drive) should theoretically be much >> faster... Many disk intensive operations seem to be faster on the IDE >> drives. Any ideas as to why this should be? > >The IDE disks are probably just simply faster. > >Don't confuse the transfer rate with the disk speed. No drives I know >of can currently hit 33 MB/s, so that's not the issue, and some recent >IDE drives are blindingly fast. If you want to check, run rawio >(/usr/ports/benchmarks/rawio) against the drives and see what speeds >it comes up with. > >Greg Just as a datapoint: http://www.storage.ibm.com/hardsoft/diskdrdl/prod/ds75gxp40gv.htm I want one. No, actually I want two. Tom Embt tom@embt.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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